Canadian trial of sublingual swallow immunotherapy for ragweed rhinoconjunctivitis

BACKGROUND: Sublingual swallow immunotherapy has been increasingly recognized as a safe and efficacious alternative to parenteral specific immunotherapy. OBJECTIVE: To determine the safety and efficacy of sublingual swallow immunotherapy ragweed allergen extract for rhinoconjunctivitis treatment starting just before and continuing through the ragweed pollen season. METHODS: This randomized, double-blind, placebo-controlled study was performed in children and adults with a documented history of allergic rhinoconjunctivitis during ragweed season at 9 Canadian allergy centers. Active treatment was standardized extract of ragweed allergen administered as sublingual swallow drops at increasing doses starting shortly before the pollen season and maintenance doses continued daily during the season. Primary efficacy variables were symptom and medication scores, and secondary variables included global evaluation of efficacy and immunologic measurements. RESULTS: Eighty-three patients were included in the safety analysis; 76 patients were included in the intent-to-treat analysis. Nine placebo recipients and 1 treatment recipient withdrew for lack of efficacy (P = .004). Nine patients in the treatment group withdrew because of adverse events, none serious (P = .003). Investigator evaluation of efficacy showed that significantly more patients improved and fewer deteriorated in the treatment group vs the placebo group (P = .047). Ragweed IgE and IgG4 levels increased significantly in treatment recipients vs placebo users (P < .001). Sneezing and nasal pruritus approached significant improvement in the treatment group vs the placebo group (P = .09 and .06, respectively). Quebec City experienced low pollen counts. Excluding Quebec City, significant improvement was seen for these 2 symptoms (P = .04). CONCLUSION: Sublingual swallow immunotherapy seems to be safe and efficacious for ragweed rhinoconjunctivitis even when started immediately before the ragweed pollen season.